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Relations And Functions

Question
CBSEENMA12034281

Find f(A), if f(x) = x2–5x –14 and straight A equals space open square brackets table row 3 cell negative 5 end cell row cell negative 4 end cell 2 end table close square brackets

Solution
Here space straight f left parenthesis straight x right parenthesis space equals space straight x squared minus 5 straight x minus 14
therefore space straight f left parenthesis straight A right parenthesis equals space straight A to the power of 2 space end exponent minus 5 straight A minus 141
Now space space space space space space space space space space space space space space straight A equals space open square brackets table row 3 cell negative 5 end cell row cell negative 4 end cell 2 end table close square brackets
space space space space space space space space space space space space space space space space space space space space straight A to the power of 2 space end exponent space equals space space open square brackets table row 3 cell negative 5 end cell row cell negative 4 end cell 2 end table close square brackets space space open square brackets table row 3 cell space minus 5 end cell row cell negative 4 end cell cell space space space 2 end cell end table close square brackets
space space space space space space space space space space space space space space space space space space space space space space space space space equals space space space open square brackets table row cell 9 plus 20 end cell cell space space minus 15 minus 10 end cell row cell negative 12 minus 8 end cell cell space space space space space 20 plus 4 end cell end table close square brackets space space equals space open square brackets table row 29 cell space space minus 25 end cell row cell negative 20 end cell cell space space space space space 24 end cell end table close square brackets
therefore straight A to the power of 2 space end exponent plus 5 straight A minus 141 equals space space open square brackets table row 29 cell space minus 25 end cell row cell negative 20 space end cell cell space space space space 24 end cell end table close square brackets space minus 5 space open square brackets table row 3 cell space space minus 5 end cell row cell negative 4 end cell cell space space space space 2 end cell end table close square brackets space minus 14 space space open square brackets table row 1 cell space space space 0 end cell row 0 cell space space space 1 end cell end table close square brackets
space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals space open square brackets table row 29 cell space minus 25 end cell row cell negative 20 space end cell cell space space space space 24 end cell end table close square brackets space plus space open square brackets table row cell negative 15 end cell cell space space space space 25 end cell row 20 cell negative 10 end cell end table close square brackets space space space plus space open square brackets table row cell negative 14 end cell cell space space space space 0 end cell row 0 cell negative 14 end cell end table close square brackets space space
space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals space open square brackets table row cell 29 minus 15 minus 14 end cell cell space space minus 25 plus 25 plus 0 end cell row cell negative 20 plus 20 plus 0 space space space end cell cell 24 minus 10 minus 140 end cell end table close square brackets space space equals space open square brackets table row 0 cell space space 0 end cell row 0 cell space space 0 end cell end table close square brackets space space space space space space space space space space
space space space space space space space space space space space space space space space space space space space space straight f left parenthesis straight A right parenthesis equals straight O space
space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space

Some More Questions From Relations and Functions Chapter

If a matrix has 24 elements, what are the possible orders it can have ? Wh'at. if it has 13 elements ?

lf a matrix has 18 elements, what are the possible orders it can have ? What, if it has 5 elements?

If a matrix A has 12 elements, what arc the possible orders it can have 7 What if it has 7 elements ?

Let A be the set of all students of a boys school. Show that the relation R in A given by R = {(a, b) : a is sister of b} is the empty relation and R’ = {(a, b) : the difference between heights of a and b is less than 3 meters} is the universal relation.

Show that the relation R in the set {1, 2, 3} given by R = {(1, 1), (2, 2), (3, 3), (1, 2), (2, 3)} is reflexive but neither symmetric nor transitive.

Show that the relation R in the set {1, 2, 3} given by R = {(1, 2), (2, 1)} is symmetric but neither reflexive nor transitive.

Give an example of a relation which is

(i) Symmetric but neither reflexive nor transitive.
(ii) Transitive but neither reflexive nor symmetric.
(iii) Reflexive and symmetric but not transitive.
(iv) Reflexive and transitive but not symmetric.
(v) Symmetric and transitive but not reflexive.

Let L be the set of all lines in a plane and R be the relation in L defined as R = {(L1, L2) : L1 is perpendicular to L2}. Show that R is symmetric but neither reflexive nor transitive.

 Determine whether each of the following relations are reflexive, symmetric and transitive :

(i) Relation R in the set A = {1, 2, 3,....., 13, 14} defined as

R = {(x, y) : 3 x – y = 0}

(ii) Relation R in the set N of natural numbers defined as R = {(x, y) : y = x + 5 and x < 4} (iii) Relation R in the set A = {1, 2, 3, 4, 5, 6} as R = {(x,y) : y is divisible by x} (iv) Relation R in the set Z of all integers defined as R = {(x,y) : x – y is an integer}

(v) Relation R in the set A of human beings in a town at a particular time given by
(a)    R = {(x, y) : x and y work at the same place}
(b)    R = {(x,y) : x and y live in the same locality}
(c)    R = {(x, y) : x is exactly 7 cm taller than y}
(d)    R = {(x, y) : x is wife of y}
(e)    R = {(x,y) : x is father of y}